Scaling silicon: These scaled-down, hexagonal silicon solar cells range from 0.25 to one millimeter across. The lines visible on some of them are metal electrical contacts.
Murat Okandan
The new cells promise to be cheaper, more efficient, and even printable.
Researchers at Sandia National Laboratories have shrunk silicon solar cells down to the micro scale, opening new possibilities for improved efficiency.
Multi-crystalline silicon, currently the gold standard for solar-cell efficiency, is expensive and produces cells that are heavy and brittle. Sandia's microscopic silicon solar cells use 100 times less material while operating with the same efficiency.
In addition to lower materials costs, the smaller scale of these cells means they could be incorporated into compact optical systems for cheaper light-tracking and concentration. Researchers might even suspend them in inks that could be printed onto plastic to make efficient, flexible silicon-solar modules.
"In microsystems, you're looking for things that become cheaper, perform better, and gain new functionalities," says Gregory Nielson, head scientist on the project.
So far, the Sandia researchers have assembled and tested a single micro solar cell as proof of principle. But they have begun testing functioning solar modules made from multiple tiny cells and are developing techniques for assembling them efficiently.
Sandia's cells are between 0.25 and one millimeter in diameter. The main benefit of manufacturing such small cells would be lower materials costs, since the tiny cells can be made about 10 times thinner than conventional ones. Ordinarily, solar cells must be 100 micrometers thick to support their surface area--typically about 15 centimeters square.
Sandia makes its cells from silicon that has been processed using conventional chemical methods. Researchers carve the cells out of this silicon using a chemical etching technique that creates negligible waste. They treat the surface of the wafer to create the electrical properties necessary for a functioning cell, then top it with metal contacts. Researchers then etch the top 10 to 20 micrometers of the wafer surface using chemicals that only eat into a particular part of the crystal structure.
The resulting cells are about 20 micrometers thick but have the same efficiency as conventional cells, converting about 14.9 percent of sunlight into electrical energy. It's also easier to make the cells in a hexagonal shape, which makes the most of the available area without wasting much silicon. "The materials savings are a big deal," says Nielson.
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Another advantage of the small cell size is that it should be much easier to produce it using crystalline silicon for greater efficiency rather than use amorphous silicon.
The biggest difficulty I see would be in the configuring the underlying substrate that would collect the charge collected by each of these micro-cells and funnel it to the storage unit, particularly when looking to produce them using an automated or self-assembly process such as with the "printing" deposition method discussed.
It is not clear whether these micro-cells are the same shape top and bottom - another complication for self-assembly techniques.
It does sound very interesting though, and would make it much easier to produce form-fitting solar cell collectors to objects. I would also like to follow the progression of this idea.
This again could be an ideal candidate for creating personal mobiles which can be printed with solar cells. For example we could have a 3 wheeled senior citizen trike with a sun shield printed with solar cells. Pedal power could be added for cloudy days.
Cheap affordable transportation for the masses
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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5 Comments
Solar infrastructure costs
This is an encouraging article.
The biggest challenge facing solar power is the cost of infrastructure. The cost and energy required to mount the cells, track the sun, potentially store the energy, get to the grid, and distribute the power to where it's needed place a huge challenge on solar power.
Reducing material cost, mounting cost, and cost and complexity of tracking are all big potential benefits. The reduced cost and complexity will make it easier to build near the point of use reducing grid and other distribution cost.
I'm interested in seeing how quickly development proceeds.
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